A core drilling machine uses a cylindrical diamond-tipped drill bit to cut a ring-shaped groove into a workpiece that is to be processed in order to create a cylindrical drill core there which can then be removed in its entirety from the drilled hole after the completion of the core drilling procedure. The material that is to be processed can be, for example, concrete, masonry, stone or the like.
Such a core drilling device and an associated method to control this core drilling device are disclosed in German Preliminary Published Application DE 10 2009 000 015. According to this document belonging to the state of the art, the acceleration along a striking axis of a pneumatically striking handheld power tool is measured. The drive output of the handheld power tool is reduced if the measured acceleration is greater than a previously set threshold value. In this context, the threshold value is set in such a way that it is greater than the maximum acceleration values that occur during the operation of a handheld power tool that is striking onto a workpiece.
Core drilling, particularly using handheld core drilling machines, is a demanding work procedure and it requires a number of different actions during the individual work phases. These include, for example, adjusting the parameters of the core drilling machine to changing conditions or else varying the advancing speed of the tool (drill bit) into the material that is to be processed. In the case of handheld core drilling machines, in contrast to core drilling machines mounted on stands, there is the additional complicating factor, namely, that users have to hold, control and guide the core drilling machine with their hands. Since even handheld core drilling machines can usually be quite heavy and since the working position is seldom very comfortable for the user, that is to say, the working position is too low, too high or even above the head of the user, many problems can occur during the core drilling procedure as the users are trying to comply with all of the important parameters while performing the numerous tasks. Particularly in the early core drilling phase, that is to say, during the so-called spot-drilling, many difficulties can arise which can have a negative impact on the entire core drilling procedure and especially on the result of the core drilling.